An acoustic wave device having a piezoelectric substrate, acoustic wave elements which are provided on the piezoelectric substrate, and a cover for sealing the acoustic wave elements is known. In the narrow sense of a SAW device, between the piezoelectric substrate and the cover, an oscillation space for housing the acoustic wave elements is formed in order to facilitate oscillation of the acoustic wave elements. Patent Literature 1 discloses an acoustic wave device in which two oscillation spaces are formed.
On the piezoelectric substrate, a plurality of lines connected to the acoustic wave elements are provided as well. The plurality of lines have portions formed thicker than the thickness of the acoustic wave element. If a cover is laid over such relatively thick portions, a gap is liable to form between the substrate and the cover and the cover is liable to easily peel off from the substrate.
Accordingly, preferably there is provided a high reliability acoustic wave device capable of suppressing peeling of the cover from the substrate and formation of a gap between the cover and the substrate even in a case where thick portions is provided at the lines.